When your ass falls asleep, in the same way that your leg or your arm does. Can occur at any time without warning. It tends to recur, and may be more properly referred to as a chronic condition as such. Reports indicate that some find it pleasant, while others don't.
Bar Narcolepsy, often shortened to Barcolepsy, is a disorder characterized by a sudden and uncontrollable urge to fall asleep while out drinking with friends. Bar narcolepsy is often triggered by excessive amounts of alcohol.
Bar narcoleptics can often be seen sleeping on couches, stairwells and in extreme cases the floor.
Bar narcoleptics are usually accompanied by friends who try and escape the attention of the bounces by holding them in and upright position and pretending to engage them in conversation.
(n) a chronic and usually hereditary sleep disorder in which the person affected will suffer spontaneous bouts of sleep (or "sleep attacks") during the day. Symptoms include: extreme sleepiness, typically followed by sleep attacks and last for fifteen minutes; dream-like hallucinations; sleep paralysis, where you cannot move when you start to fall asleep or just after you wake up; and cataplexy, which is an abrupt loss of muscle tone (basically, your muscles "fail you").
The disorder is not fatal, but can be depending on the situation you find yourself having a sleep episode. There is no cure for narcolepsy at the moment.